This is evolution that will likely fail due to the fish being more visible to predators and more likely to be killed before it gets to breeding age. Now if you take this bass and breed it with other bass like this, or even a normal colored bass for that matter. you will get more like it, and some normal ones. keep breeding the colorful ones together and we could eventually be fishing for 'koi' largemouth.
someone pointed out that this is known as 'piebald' pigmentation. it's a natural pigmentation variation along the lines of albinism (lack of pigment), melanism (all black pigment), amelanism (lack of black pigment) etc.